Which of the relatively cheap filaments is the most hygroscopic. I want to do an experiment regarding filament drying so need a filament that will hoover up moisture. Probable won’t print with it but have got my data sensors up and running and need a test object.
PA, PVA, and TPU.
These are generally considered the most hydrophobic, in that order.
My guess is that TPU will meet your needs.
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Bambu PETG HF is wet out of the bag.
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I didn’t find this, although BL makes a big thing of it.
Each time people tell me I must dry my filaments before use, it confuses me as I have only had to dry filaments twice since I started printing 4 years ago.
I even have one of those dryer boxes which at the time cost a lot of money and it has been used twice.
My humidity sensors tell me it is usually 68-71% humid in my house. Yet, I do not experience what everyone else appears to live with.
This filament spool will be ruined as part of my experiment. I want to run an RTD, Thermocouple or other temperature sensor into the middle of a full spool to see how long it takes the spool center filament to climb up to full drying temperature. The filament has some level of thermal conductivity and heat but not blown air has to migrate across the filament cross-section, the filament give up it’s moisture, then get that moisture to the outside of spool and purge it to atmosphere.
You may have seen in another post that I bought a Sunlu S4 filament Dryer. If you have not seen one, it is a big single box but constructed to take two spools in each half and each half chamber has 4 ports you can use to bring filament out of and run to an extruder. 8 ports total which if you do not have filament coming out, the heated “wet” air will blow out of. It also has baskets for desicant in each half. The way I read the instructions, even with all 4 spools supplying filament you still have 4 open ports exhauting wet air. I also have humidity sensors so I am going to take one of those dryer ports and blow it across the humidity sensor and plot it all to get a sense of how long it takes to get a spool to full temperature AND dry it.
That’s weird… I’ve certainly heard the popping at the nozzle of the moisture boiling and always dry my filament just to be consistent.
Whatever setup you’ve got, stick with it if it’s working for you. Lucky you… 
What is weird? I just want to capture the environment inside housing of my P1S
My question is based on the premise that you are trying to dry the filament prior to printing but a spool of filament is this big mass of PLA, PETG, PA6, that only sees ACTIVE airflow only the outside MAYBE 3 - 4 layers then it is pure conductive heat.
So how long does it take to get the entire spool up to a temperature that will drive off the moisture dead center of the spool?
I’m a 100% believer in dry filament will print better than damp filament. What I think though is it would take days, not hours, to dry a full 1kg spool of PETG filament. I have sensors galore,
It’s certainly an interesting question. Actual data is better than the filament manufacturers recommendation. Looking forward to your results.
As my filament is generally dried in the heated dryer, and the filament is removed from the surface of the roll and you can only print at a certain rate which means the surface filament is constantly being dried, then for all but the most difficult fillaments, that’s probably good enough. The standard Sunlu dryer with built in fan is getting me down to 10-12% humidity at 46degC There are better and more expensive dryers on the market, but that level of drying gives me good prints.
I already have some of the sensors mounted and reading in the bottom of the P1S and want to put some in the upper end of the printer and another set in the AMS. I retired in mid-2021 so have ample free time and it is a real-world item.
What gave me the initial kick was a klick-bait YouTube headline to the effect of “I was poisoned printing ABS” or something along those lines. After watching the video it was mostly click-bait but these printers are melting plastic which can be quite toxic if it should start burning and some of the “I scorched my hotend” stories were also a motivator.
I can certainly see it on the trends of temp and humidity when I start a print.
Funny, Igor put this out this morning.
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About what I have been thinking.
I’ve done the same exact test but with a different material being tested. Scale was a several hundred dollars, the table the scale sat on was topped with a 6 inch thick piece of granite and scale was inside an enclosure but the tests were legal documents that we sent to the state environmental agency. A real PITA.
A lot depends on what you, me, whoever, considers acceptable.
My first experience with Bambu Lab PETG was that it was bumpy which the consensus being that it was too wet. There’s a big BUT in there though. I did not and would not have rejected the “bumpy” prints as unacceptable. The person I made them for sure didn’t. He was ecstatic.
I did go out and buy the Sunlu S4 based on the Bambu forum feedback and it absolutely improved the surface quality of my foray into PETG.
The instrumentation I am putting in and on the P1S are inexpensive but of significantly better accuracy than these round relative humidity/temperature instruments one can buy from Amazon or AliExpress.
Once I get my various instruments chosen, permanently installed, it is my intent to make them publicly viewable. for those that are interested but a long way from that yet. My comment earlier in thread about drilling a spool and sticking an RTD or thermocouple in in the drill hole are just for my curiosity, just like the guy in video putting PETG in a bucket of water.
Plastic seems solid but in microscopic level, it is like multiple strands of hair bundle together. Unless the molecules of plastic are packed tight like in metal crystal structure, it will never be true isolated from moisture.
Same for plastic bag that your filament spool come in. The H2O molecule will attach to the outmost polymer chain and then that chain will give H2O to the inner polymer chain. The process will continue until the it reaches to the air inside the bag, and eventually get into the filament. This process is slow and depends on moisture level and temperature of where you store your sealed bag of filament.
Only exception is when filament shipped with aluminium coated bag. Same goes for moisture sensitive electronic devices that shipped in aluminium coated bag (mouser, digikey sometimes ships micro-chip in those bag, but not LCSC)
Anyhow, you never know if the filament they make was wet before packaging or wet after packaging. Never assume it is dry when you open a new bag of filament.
But I admit I rarely have to dry my filament when I cut open a new bag
I don’t dispute filament getting moisture in it. I’m more dubious about ones ability to dry more than a few layers deep on the spool. I’ve bought several reusable spools from Bambu but I suspect an individuals most optimal crack at drying the filament is when he purchases as a refill and puts the unspooled filament in the dryer for a day before putting it on a spool for use
I understand you. Those words are just for general readers who stumble upon the moisture problem and happen to read this thread.
I had similar feeling, running oven at 80deg for 8 hours still doesn’t feel enough to drive moisture out completely from the inner layer near the core of the roll.
I once put 1 PA roll inside sovol dry box for 12 hours or maximum time I could set but seem it did nothing to the PA roll, it still delaminated and popped off the bed and made spagetti.